Building a 4 Stroke that competes with KTM 50s?

Hey guys,

I am looking into upgrading my son's '04 CRF50 to try and compete with the KTM 50s in the PW4-6 classes. I know that it might be easier to just buy him a new KTM Senior but I don't want to spend 3K on a bike that I have to fiddle with all the time (i.e., clutches, new parts, etc.).

The CRF is lagging behind the KTMs in 3 main areas: power, suspension, and weight.

I figure since the big 4s get to run twice the CCs then, I should be able to run at least a 100 cc 4 (maybe a 110) against the 2 stroke 50s.

My question is would an 88 big bore kit or a 110 kit make as much HP as the KTM 50s? If so, are there any shocks and forks that can be adjusted for a kid weighing 60-70lbs? Lastly, are the aftermarket frames and swingarms significantly lighter than the stock components?

I was thinking that I could also throw a 3-speed manual transmission on it too. I just think that it would be really cool to have a little thumper out there on the track banging bars with the 2-strokers. What do you guys think? :naughty:

You can build a xr50 that will lay a whoopin down on a xr200 if you want.

A 88 Race head motor should be plenty to lay it down on those KTM 50's no problem.

I used to Run a 88 Racehead before I went to a 108 and I weighing 120lb's could run with 80's, now with the 108 Ill really be flying hehe. has all the motor stuff you should need, send me a PM as I can get you a better deal on them.

Suspensio wise, some BBR SP5 forks with stock xr70 springs or one stiff BBR and one stock 70 springs should make the front end nice for a little guy. For the rear, I would say a +2 swingarm, I have a nice aluminum Foes Racing swingarm for sale for $200, $150 less than new, and also probably contact Works Performance and they can build a shock to exactly suit his weight for about $300.

I have an 88cc Takegawa R-stage setup that you could put on that bike and whoop them bad. I took it off to go to a larger setup. New they are 880 (990 when I bought it)before another 200 for a cam from classic honda. I will let them go for 600 plus shipping. I will also throw in brand new rings and gasket set. If you are interested let me know and I can save you some money. As for the suspension stuff sounds like i would go with the swingarm he has. I have a set of stock forks with HD springs that I would take 90 for.




Lol, not even close to how much Ill save him. I can sale him a 108 stroker for less than that.

HONDA? I was just trying to clean out the parts in the garage and save someone some money. If you have Honda bottom end 108's for less than 600 bux I may be in the market for one...

well tb 88 race head and stroker kit is 108 (thats prolly what he is talkin about) and its probably less than 600...

Yup, complete Hondatrailbikes 108 strokers for under $600.

Do you really need a oil cooler with the 108 kit, i have heard both answers and looking for the right... thanks

Sorry, answered my own question while browsing TB web site....... Jester, does the TB 108 kit come with a bigger head? what power difference is there between the 108 and the 88 w/race head? Thanks

I was thinking that the way he answered the question he meant a turn key motor.... Granted you can get a 108 stroker setup for under 600 but how does the TB stuff stand up to Takegawa R-Stage. Just asking cause I have never used TB parts.

TrailBikes parts are great, before upping to the 108 I had the 88 Race head in for over a year without a single problem, the quality is identical to Takegawa or Kitaco.

Yes the TB 108 comes with a Race head and the power diff between the 88 and the 108 is amazing. It will easily walk away from the 88, there is just so much more torque and power everywhere.

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